1. Field of the Invention
The invention relates to a self-pumping hydropneumatic vibration damper with level control, especially for motor vehicles. The vibration damper includes a damping oil-filled working cylinder under the pressure of at least one gas cushion, which is located in a high-pressure chamber and acts as a spring, the working cylinder being divided into two working spaces by a working piston mounted on a piston rod; and a piston pump driven by sprung movements of the vehicle to convey damping oil from a low-pressure chamber into the working space connected to the high-pressure chamber.
2. Description of the Related Art
Self-pumping hydropneumatic vibration dampers with internal level control are already known (e.g., U.S. Pat. Nos. 5,826,863 and 6,651,547), in which the working piston divides the working cylinder into two working spaces and in which the piston rod and a pump rod together form a pump cylinder, which conveys oil from a low-pressure chamber to the working space connected to the high-pressure chamber under the action of the sprung movements caused by irregularities in the pavement. Depending on the position of the working piston in the working cylinder, a regulating opening connects the high-pressure chamber to the low-pressure chamber and thus, when the vehicle is unloaded, the vehicle body returns to its normal level again. With this type of vibration damper, however, the piston pump requires both a hollow piston rod and a pump rod.